Conventionally, a resin-sealed type and a sealed and airtight type are known as a package utilized for a semiconductor element.
The resin-sealed type semiconductor device has a structure which embedded directly the semiconductor element mounted in a leadframe in the resin by using a transfer mold etc., and is widely used by the advantage, such as low cost, being suitable for mass production, and a miniaturization being possible.
The sealed and airtight type semiconductor device has a structure which performed in hollow airtight maintenance of the semiconductor element mounted on a base substance composed of conductive materials, such as copper. Although the cost is higher compared with the resin-sealed type semiconductor device, the sealed and airtight type semiconductor device is used when high reliability is required because of excellent in airtightness.
In the sealed and airtight type package, it is known about an example of package mounting a semiconductor element directly on the heat radiation body composed of metal, and including an input/output terminal portion having convex feed through structure.
It is preferable that a characteristic impedance of feed through is 50Ω. However, in the sealed and airtight type package, the characteristic impedance of feed through is reduced due to the feed through being surrounded by a grounded metal outer wall. Although the characteristic impedance can be reached to 50Ω by forming a signal line of feed through to be narrow, an electric power capability is reduced due to the narrowed signal line, because a function of the feed through is to allow electric current and signals to pass through.